Considering the number of headers we have, it is a good idea to
avoid possible problems. For details, you may read:
http://en.wikipedia.org/wiki/Include_guard
All headers should be ok now.
The new shutdown.h file includes the shutdown modes and the functions
to shutdown Window Maker.
The function definitios were moved from funcs.h and the struct WShutdownMode
from WindowMaker.h.
Now, externs are not needed, only include shutdown.h